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CN 11-1958/O4
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Multiple spatial coherence resonances induced by white gaussian noise in excitable network composed of Morris-Lecar model with class Ⅱ excitability
Li Yu-Ye,Jia Bing,Gu Hua-Guang
Acta Physica Sinica, 2012, 61 (7): 070504
WLW mass model in nuclear r-process calculations
Li Zhu,Niu Zhong-Ming,Sun Bao-Hua,Wang Ning,Meng Jie
Acta Physica Sinica, 2012, 61 (7): 072601
Investigation on the application of phase-attenuation duality to X-ray mixed contrast quantitative micro-tomography
Liu Hui-Qiang,Ren Yu-Qi,Zhou Guang-Zhao,He You,Xue Yan-Ling,Xiao Ti-Qiao
Acta Physica Sinica, 2012, 61 (7): 078701
Acta Physica Sinica  
  Acta Physica Sinica--2012, 61 (7)   Published: 05 April 2012
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Experiment progress of ablative Rayleigh-Taylor instability based on X-ray framing camera

Cao Zhu-Rong,Miao Wen-Yong,Dong Jian-Jun,Yuan Yong-Teng,Yang Zheng-Hua,Yuan Zheng,Zhang Hai-Ying,Liu Shen-Ye,Jiang Shao-En,Ding Yong-Kun
Acta Physica Sinica. 2012, 61 (7): 075213 doi: 10.7498/aps.61.075213
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Using high dynamic range X-ray framing camera, the radiation driven ablative Rayleigh-Taylor instability facing backlight radiography on SHENGUANH (SG) II device is studied. In the SG II that has eight beams with the 2 ns laser pulse and the ninth beam for Mo backlight, two-dimensional space-time ablation RT growth process for the cycle 20 μm and the initial perturbation 1 μm are observed clearly, and the non-linear growth process is also observed by the doping Br ratio of 1.1% in samples. The result lays a good foundation for quantitative characterization and numerical simulation of RT instability in inertial confinement fusion (ICF) experiments.


Homotopy analysis solution of point reactor kinetics equations with six-group delayed neutrons

Zhu Qian,Shang Xue-Li,Chen Wen-Zhen
Acta Physica Sinica. 2012, 61 (7): 070201 doi: 10.7498/aps.61.070201
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Homotopy analysis method is a new method to form approximate analytical solution for non-linear system by using various base functions, which is different from traditional analytical methods. So far, the analytical solution of the point reactor neutron kinetics equations with six-group delayed neutrons has not been obtained yet. In this paper the homotopy analysis method is employed for solving the point reactor neutron kinetics equations with six-group delayed neutrons. The series analysis solutions are obtained using the homotopy analysis method, and the relevant algorithm is given and analyzed. The results show that the computation time and accuracy satisfy the engineering requirements. This analysis method can be applied to the design, the analysis and the simulation of reactor control.

Simulation of imaging spectrometers degraded by satellite vibrations

Tang Qiu-Yan,Tang Yi,Cao Wei-Liang,Wang Jing,Nan Yi-Bing,Ni Guo-Qiang
Acta Physica Sinica. 2012, 61 (7): 070202 doi: 10.7498/aps.61.070202
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Instability of satellite platform will seriously affect the quality of spectral imaging. The degradation mechanism of interferential and dispersive imaging spectrometers caused by satellite vibrations is studied in this paper. A simulation algorithm of degradation based on differential dynamic spectral imaging is presented. And the concept of mean mixing ratio (MMR) is proposed, which builds the bridge between the parameters of satellite vibration and the influences on spectral imaging. The quantitative relationship between them is also deduced in detail. Spectral degradation results are simulated by taking the typical spectra and the generated spectrums of surface features as the ideal original data. Simulation results show that the effects caused by pitch and roll are much greater than that by yaw, and the vibrations affect not only spatial resolution but also spectrum, and the regions of rich species are influenced seriously.

Generalized variational principles for three kinds of atmospheric waves

Song Jun-Qiang,Cao Xiao-Qun,Zhu Xiao-Qian,Zhang Wei-Min,Zhao Jun
Acta Physica Sinica. 2012, 61 (7): 070401 doi: 10.7498/aps.61.070401
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The semi-inverse method is proposed by He to establish generalized variational principles for mathematical and physical problems, in which the variational crisis brought by the Lagrange multiplier method can be eliminated. with He's semi-inverse method, a family of variational principles is constructed for Rossby wave, atmospheric acoustic wave and gravity wave respectively. The obtained variational principles have also proved correct.

Improved particle filter in data assimilation

Leng Hong-Ze,Song Jun-Qiang,Cao Xiao-Qun,Yang Jin-Hui
Acta Physica Sinica. 2012, 61 (7): 070501 doi: 10.7498/aps.61.070501
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Owing to the fact that standard particle filter and ensemble Kalman filter can not efficiently represent the posterior probability density function (PDF), an improved particle filter is proposed. In this algorithm, an innovation step is introduced after the prediction step, and the analyses of non-observation time and observation time are treated separately. The numerical simulations of a low- and a high-dimensional systems show that this new particle filter can follow the true state of a highly nonlinear non-Gaussian system very well.

The oscillations of a switching electrical circuit and the mechanism of non-smooth bifurcations

Wu Tian-Yi,Zhang Zheng-Di,Bi Qin-Sheng
Acta Physica Sinica. 2012, 61 (7): 070502 doi: 10.7498/aps.61.070502
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The complicated dynamical evolution of a circuit system composed of two Rayleigh-types subsystems, which are switched by a periodic switch and a threshold controller, is investigated. Through the analysis of the subsystem equilibrium points, the conditions for Fold bifurcation and Hopf bifurcation in the parameter space are given respectively. The distribution of the generalized Jacobian eigenvalues varying with auxiliary parameter at the switching boundary is presented. Then the possible bifurcation behaviors of the system at the switching boundary are obtained. The mechanisms of the different behaviors of the system are discussed. It is pointed that the trajectories of the system have two kinds of turning points, which are determined by the periodic switch and the threshold controller respectively. Meanwhile, the multiple collisions between the trajectories and the non-smooth boundary may lead the system to change from chaos to period-adding bifurcation.

Design and research of chaotic vibration isolation system under the condition of small displacement

Jiang Guo-Ping,Tao Wei-Jun,Huan Shi,Xiao Bo-qi
Acta Physica Sinica. 2012, 61 (7): 070503 doi: 10.7498/aps.61.070503
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A chaotic vibration isolation device under the condition of small displacement is designed according to the chaotic vibration theory.The device can generate strong nonlinearity under small displacement. The linear part and the nonlinear part are completely separated. The overall stiffness, the ratio of linear term to nonlinear term can be easily adjusted. The engineering application scope of the device turns wider. The numerical simulation is carried out with specific parameters. The design is confirmed.

Multiple spatial coherence resonances induced by white gaussian noise in excitable network composed of Morris-Lecar model with class Ⅱ excitability Hot!

Li Yu-Ye,Jia Bing,Gu Hua-Guang
Acta Physica Sinica. 2012, 61 (7): 070504 doi: 10.7498/aps.61.070504
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To study the effect of noise on the network and the influence of noise on the spatio-temporal behaviors of the network, a homogeneous network of excitable cells is constructed, in which the classical Morris-Lecar neuron model behaves as a unit by electric coupling to neighbouring ones. The deterministic behavior of each unit is a resting state corresponding to class Ⅱ excitability. Under the action of white Gaussian noise in the network, spiral wave can be induced within a large range of noise intensity, while disordered spatiotemporal structure is induced within a certain small intensity range. With the increase of noise intensity, spiral wave is characterized by a transition back and forth between simple structure and complex structure, or appears alternately with the disordered structure. By calculating spatial structure function and signal-to-noise ratio (SNR), it is found that the SNR of spiral wave with a simple structure is higher and the SNR becomes lower when the spiral wave has a complex or an even disordered structure. The SNR curve shows that multiple peaks appear with the increase of noise intensity, which indicates that white Gaussian noise can induce the multiple spatial coherence resonance in an excitable cellular network, and suggests that there are many opportunities to select diverse intensity noises to be rationally used in a realistic excitable system.

Synchronizations of chaotic neuronal networks under different couplings

Wu Wang-Sheng,Tang Guo-Ning
Acta Physica Sinica. 2012, 61 (7): 070505 doi: 10.7498/aps.61.070505
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The synchronization of a two-dimensional (2D) neuronal network is investigated, based on the dynamical model of Hindmarsh-Rose neuron. In order to know the effects of different types of coupling on the synchronization of a network, we propose three coupling schemes. They are the general feedback coupling, the hierarchical feedback couplings with and without local mean field. The numerical results show that when the neighbor coupling strength is small, the hierarchical feedback couplings with and without local mean field can achieve local and global synchronizations of the network, whereas the general feedback coupling cannot achieve global synchronization. Different couplings generate different patterns in the corresponding network, so that the processes of the transition from asynchronization to synchronization in the networks are different. With the increase of coupling strength, the synchronization in the network with the general feedback or hierarchical feedback couplings is suddenly established, and the networks exhibit different coherent patterns that are aperiodic before the global synchronization occurs. However, the network with hierarchical feedback couplings and local mean field exhibits the different synchronous processes. The neurons in the same layer first achieve the transition from bursting synchronization to global synchronization, leading to the formation of target wave. Then, the synchronization region gradually expands from the center of the network. Finally, the whole networks can achieve synchronization. These results show that the lossless signal transmission can be achieved only if the appropriate coupling is applied. In addition, we find that the hierarchical feedback coupling with local mean field can facilitate synchronization.

Numerical simulation of dynamic scaling behavior of the etching model on randomly diluted lattices

Xie Yu-Ying,Tang Gang,Xun Zhi-Peng,Han Kui,Xia Hui,Hao Da-Peng,Zhang Yong-Wei,Li Yan
Acta Physica Sinica. 2012, 61 (7): 070506 doi: 10.7498/aps.61.070506
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Surface roughening has been extensively studied in many fields of science and technology. In order to investigate the influence of imperfection of the randomly diluted lattices on dynamic scaling behavior of the surfaces, the etching model growing on diluted squares is simulated by kinetic Monte Carlo (KMC) simulation. It is found that although the scaling behavior of the etching model can be affected by imperfections of the randomly diluted lattices, the roughness and the growth exponent are larger than those of the growth on perfect squares. The scaling behavior still satisfies the Family-Vicsek dynamic scaling. In addition, the finite system size effect of the randomly diluted lattice is also calculated and analyzed.

A feedback neural network with weights of sinusoidal functions

Li Cheng,Shi Dan,Zou Yun-Ping
Acta Physica Sinica. 2012, 61 (7): 070701 doi: 10.7498/aps.61.070701
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A new feedback neural network model is proposed. The network has the sinusoidal basis functions as its weights. Neuronal activation function is a linear function. The network connection form is feedback structure. An energy function is defined for the feedback neural network. And then, the network stability issue in operation is analyzed. In the Liapunov sense, the proposed feedback network stability is proved. During the operation of the network, the network states are changed ceaselessly but network weights vary according to time-dependent sinusoidal law. As the network state changes continuously, its energy will be reduced. Finally, when network comes to a stable state, its energy arrivs at a minimum value. The network is particularly suited for the adaptive approximation and the detection for periodic signals because of its sinusoidal basis function weights. It is, in practice, a new and effective way for periodic signal detection and processing. The very good detection results are obtained in the detection of power system voltage sag characteristics. Simulation examples show that the dynamic response speed of the network is very high.

Characterization of the p-type ZnO solid solution by doping Li under high pressure

Qin Jie-Ming,Tian Li-Fei,Jiang Da-Yong,Gao Shang,Zhao Jian-Xun,Liang Jian-Cheng
Acta Physica Sinica. 2012, 61 (7): 070702 doi: 10.7498/aps.61.070702
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In this paper, stable Li-doped ZnO solid solution (ZnO: Li) is successfully prepared by sintering the mixture of ZnO and Li2O powders under a pressure of 5 GPa and at temperatures between 1200 ℃ and 1500 ℃. It is found that the high pressure and temperature conditions have significant effects on the electrical conductivity and the structure of the ZnO solid solution. The best p-type ZnO doping 4.5 at.% Li with a resistivity of 3.1× 10-1Ω·cm, carrier concentration of 3.3× 1019cm-3, and mobility of 27.7 cm/V·s is achieved at 1500 ℃. The p-type conduction formed in ZnO is due to acceptor formed by one substitutional Li atom at Zn site, which has an acceptor level of 110 meV. Furthermore, the effects of pressure on formation and electrical properties of the p-type ZnO are discussed.

Research on the mode competition in a w-band lossy ceramic-loaded gyrotron backward-wave oscillator

Du Chao-Hai,Li Zheng-Di,Xue Zhi-Hao,Liu Pu-Kun,Xue Qian-Zhong,Zhang Shi-Chang,Xu Shou-Xi,Geng Zhi-Hui,Gu Wei,Su Yi-Nong,Liu Gao-Feng
Acta Physica Sinica. 2012, 61 (7): 070703 doi: 10.7498/aps.61.070703
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Mode competition induces non-stationary oscillations during the operation of a gyrotron backward-wave oscillator (gyro-BWO), which severely reduces its tunable bandwidth and output power. Self-consistent nonlinear theory is used to study the modes-competition mechanism of a W-band fundamental TE01 mode gyro-BWO. Tapered non-resonant interaction circuit structure and loading lossy ceramic are employed to suppress the competing modes, as a way of preventing non-stationary oscillation in the circuit. Systematically optimized interaction circuit is capable of suppressing all the competing modes and can stably operate in the fundamental axial mode of the TE01 mode. Calculation indicates that a peak power of 105 kW and a -3 dB tunable bandwidth of 5.4% are attainable. This is meaningful and provides a theoretical foundation for developing broadband millimeter gyro-BWOs in the applications of counter-measure system, non-destructive detection, plasma diagnosis, material processing, and so on.

Theoretical analysis on stationary Gaussian random noise in narrowband Fourier transform spectrometer

Lü Jin-Guang,Liang Jing-Qiu,Liang Zhong-Zhu
Acta Physica Sinica. 2012, 61 (7): 070704 doi: 10.7498/aps.61.070704
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The spectral resolution can be increased by detecting the optical signal in a narrowband spectrum for the Fourier transform spectrometer based on spatial modulated in our study. In this paper, to study the effect of the radiant source on the interference system, we regard the radiant noise as a narrowband stationary Gaussian random process. Using the linear system analysis method and the statistical theory, we deduce the input signal-to-noise ratio (SNR) and the output SNR after the optical signal and the radiant noise have passed through the interference system. Then we simulate the system and compare the obained result with a narrowband rectangle spectrum, and obtain the SNR gains along the optical path difference (OPD) in different autocorrelation degree and cross-correlation degree values. The simulation result indicates that the SNR gains at different OPDs in the correlation degree space each are a monotonic smooth surface. The SNR gain maximum moves along the radius and the contour of the correlation degree circle, and it returns to the initial position. after an OPD According to the analysis of the SNR gain, the autocorrelation degree and cross-correlation degree values can be controlled in a certain area, which can serve as a criterion for the design and the test of the radiant source.


WLW mass model in nuclear r-process calculations Hot!

Li Zhu,Niu Zhong-Ming,Sun Bao-Hua,Wang Ning,Meng Jie
Acta Physica Sinica. 2012, 61 (7): 072601 doi: 10.7498/aps.61.072601
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The rapid neutron-capture process (r-process), which is an interdisciplinary field of astrophysics and nuclear physics, is bound up with various characteristics of thousands of neutron-rich exotic nuclei, such as nuclear masses, and the relevant reactions. By employing the WLW microscopic-macroscopic nuclear mass model developed recently, the solar r-process abundance distribution is well reproduced in the classical r-process approach. In comparison with the well known FRDM model, the present calculation better pictures the nuclear region of A≈135 and A≈180, and especially avoids the abundance peaks at A≈135 often obtained in other calculations. The improvement in the r-process calculation may indicate a more suitable description of the evolution of shell structure and symmetry energy towards the drip line in the WLW model.

Outgassing property of carbon nanotube cathode with intense pulsed emission

Shen Yi,Zhang Huang,Yang An-Min,Xia Lian-Sheng,Liu Xing-Guang
Acta Physica Sinica. 2012, 61 (7): 072901 doi: 10.7498/aps.61.072901
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In order to study the properties of the carbon nanotube(CNT) cathode with intense pulsed emission, the outgassing property of cathode is investigated on the 2MeV linear induction accelerator(LIA) injector. Results show that the cathode has a capability of desorbing gases from the CNT cathode under pulsed high voltage. The outgassing plays an important role in the formation of the cathode plasma. The amounts of outgassing for the several experiments are estimated to be 0.08–1.12Pa·L, the corresponding ratios between outgassing amount and electron number are roughly calculated to be in a range of 254–203atoms/e- by numerical integral of pressure, showing that the cathode plasma is weakly ionized. The relationship between diode voltage, emission current density, outgassing amount, and the outgassing molecule number per electron are analyzed.

Study of magnetic proton recoil technology for measurement of deuterium-tritium neutron spectrum

Zhou Lin,Jiang Shi-Lun,Qi Jian-Min,Wang Li-Zong
Acta Physica Sinica. 2012, 61 (7): 072902 doi: 10.7498/aps.61.072902
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A kind of fusion dianostics based on proton recoil method and magnetic analyzing technology is introduced. It can be used for the accurate diagnoses of plama tempreture, fuel density and neutron yield. A prototype is designed, using a high-powered Nd-Fe-B permanent dipole for magnetic analyzer, and proton position distribution in the focal plane is measured by CR-39 trajectory detector or PIN detector. The system is calibrated with a 239 Pu source, and a corresponding particle transport simulation program is worked out. The performance of the spectrometer is investigated with the Monte Carlo simulation, and neutron experiments are taken on the K-400 accelerator.

Error analysis of four-quadrant-based tracking sensor when dead zone is inevitable

Ma Xiao-Yu,Mu Jie,Rao Chang-Hui
Acta Physica Sinica. 2012, 61 (7): 072903 doi: 10.7498/aps.61.072903
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Based on the basic principle of four-quadrant-based tracking sensor, the energy detecting rate, centroid detecting error and the displacement sensitivity of four-quadrant detector caused by noise or dead zone are analyzed in detail. The tracking error formula of four-quadrant-based tracking senor is put forward theoretically and verified experimentally. The results show that when the noises are constant, the tracking error of four-quadrant-based tracking senor depends on the ration between the width of Gauss facula and the width of dead zone of four-quadrant detector.

The study of time-resolved measurement using ICCD positioning cosmic rays

Lü Qi-Wen,Zheng Yang-Heng,Tai Cai-Xing,Liu Fu-Hu,Cai Xiao,Fang Jian,Gao Long,Ge Yong-Shuai,Liu Ying-Biao,Sun Li-Jun,Sun Xi-Lei,Niu Shun-Li,Wang Zhi-Gang,Xie Yu-Guang,Xue Zhen,Yu bo-Xian
Acta Physica Sinica. 2012, 61 (7): 072904 doi: 10.7498/aps.61.072904
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Double layers of 150 mm?150 mm plastic scintillator arrays are used to locate the cosmic ray. Both layers of arrays are read out by wavelength-shifting fibers, which are bundled and coupled to image intensifier and ICCD camera. The light signal is delayed more than 200 ns by the image intensifier, so the ICCD can be pre-triggered by an external fast coincident signal. This cosmic ray positioning system is used to measure the time resolution and photon transfer time of the time-of-fly detector for the common test platform based on cosmic ray. Compared with traditional cosmic rays test, the data-taking efficiency of this system increases more than 30 times because of multi-point readout and higher position resolution. The test results show that the time resolution of the time-of-fly detector is better than 200 ps, which satisfies the requirement of the common platform based on cosmic ray.


Hydrogen storage capacity of Y-coated Si@Al12 clusters

Huang Hai-Shen,Wang Xiao-Man,Zhao Dong-Qiu,Wu Liang-Fu,Huang Xiao-Wei,Li Yun-Cai
Acta Physica Sinica. 2012, 61 (7): 073101 doi: 10.7498/aps.61.073101
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The adsorption property of hydrogen molecules on YmSi@Al12 (m=1–3) cluster is investigated using the density functional theory. The results show that yttrium atoms do not suffer from clustering on the Si@Al12 cluster. The 18-electron rule can be used to design these systems, and Si@Al12 cluster coated with three yttrium atoms can adsorb 16 H2 molecules with a gravimetric density of up to 5.0 wt%. The calculated adsorption energy of 0.324-0.527 eV/H2 molecule is suited for reversible hydrogen storage in near-ambient conditions.

Moment method for strain analysis and its application in molecular dynamics

Lu Guo,Wang Shuai-Chuang,Zhang Guang-Cai,Xu Ai-Guo
Acta Physica Sinica. 2012, 61 (7): 073102 doi: 10.7498/aps.61.073102
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It is necessary to investigate the characteristics and the evolution law of metal deformation by using the appropriate strain analysis method. The deformation of metal is complex, so there exists no useful method to amalyze the local deformation characteristics and to describe the global equivalent deformation of deformed metal. In this paper, we propose a statistical moment method of strain analysis. Statistical moment method builds up the relationship between micro quantities and macro strain. For instance, it is used to study the deformations of monocrystal under uniaxial load and the nanocrystalline under shear and shock, showing that moment method can not only describe and evaluate the local and the global deformation of metal but also distinguish elastic and plastic deformation by nonuniform coefficient. Moment method is a general and effective way to investigate the deformation mechanism of complex structure material.

First-principles study on the Li-storage performance of silicon clusters and graphene composite structure

Wu Jiang-Bin,Qian Yao,Guo Xiao-Jie,Cui Xian-Hui,Miao Ling,Jiang Jian-Jun
Acta Physica Sinica. 2012, 61 (7): 073601 doi: 10.7498/aps.61.073601
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This paper focuses on the Li-storage performances and the stabilities of the hybrid structure of different lattice planes of the silicon clusters and graphene by the first-principles theory. In this paper, we calculate the binding energy, the adsorption energy, and the PDOS of the hybrid structure of the different heights and sizes of the silicon clusters and graphene. We figure out that strong Si-C bonds between the silicon cluster and graphene can form. Especially, the hybrid structure of the silicon clusters with plane (111) and graphene performs best with the highest formation energy and the outstanding stability. According to the calculation of Li-absorption energy, we conclude that the location of the silicon cluster near the graphene has higher possibility and higher absorption energy of the Li storage, owing to the charge transfers between lithium and carbon, and between lithium and silicon. Because the graphene is used, the deformation of the interface of the silicon cluster can be obviously reduced during the absorption of Li, which brings about a good future for the hybrid structure used as the battery anode materials.


Effects of an external magnetic field on multipactor on a dielectric surface

Cai Li-Bing,Wang Jian-Guo,Zhu Xiang-Qin,Wang Yue,Xuan Chun,Xia Hong-Fu
Acta Physica Sinica. 2012, 61 (7): 075101 doi: 10.7498/aps.61.075101
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The dielectric surface breakdown has become a major factor of restricting the output power of high power microwave source. And the multipactor is the key phase of the process of the dielectric surface breakdown. In this paper, the multipactors in external magnetic fields with different strengths are simulated by using the particle-in-cell method. And the effect of the external magnetic field on multipactor is also studied. The results show that when the external magnetic field reaches a certain value, the multipactor is suppressed in the half time of the microwave transmission. So the power capability can be increased to more than four times through the suppression of the multipactor by the external magnetic field under the ideal condition.

The effect of the divertor operation regimes on the plasma parallel flow in the edge of a tokamak

Ou Jing,Yang Jin-Hong
Acta Physica Sinica. 2012, 61 (7): 075201 doi: 10.7498/aps.61.075201
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Based on the variations of the static pressure along the magnetic field line in different divertor operation regimes, the effects of the divertor operation regimes on the plasma parallel flow at the edge of a tokamak are investigated using a one-dimensional fluid model. In low recycling regime, the variation of the static pressure along the field line is obvious from the scrape-off layer (SOL) region near the X-point, and the variation tendency is the same as that of the density. The Mach number of the plasma parallel flow increases along the magnetic field line and the variation is from gentle to sharp. In high recycling regime, the static pressure does not change much except in the near divertor plate region, as a result, the Mach number of the plasma parallel flow varies gently in the SOL region and the most of the divertor region, and it increases rapidly in the near divertor plate region. The variation of the static pressure in weak divertor detachment regime is similar to that in high recycling regime, but the static pressure shows decrease tendency in the SOL region near the X-point, consequently, the Mach number of the plasma parallel flow at X-point is larger than that in high recycling regime. In strong divertor detachment regime, static pressure decreases obviously in the SOL region and away from the divertor plate region, where the static pressure decreases rapidly, and a high Mach plasma parallel flow is observed. Static pressure decreasing while dynamic pressure increasing to keep the total pressure conservation is shown to be a possible cause of the high Mach parallel flow.

The effect of gas puffing on plasma during slide-away discharge in the HT-7 tokamak

Lu Hong-Wei,Zha Xue-Jun,Hu Li-Qun,Lin Shi-Yao,Zhou Rui-Jie,Luo Jia-Rong,Zhong Fang-Chuan
Acta Physica Sinica. 2012, 61 (7): 075202 doi: 10.7498/aps.61.075202
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In tokamak plasma, the discharge will turn into “runaway” discharge from normal discharge if the plasma density becomes very low. The discharge will enter into “slide-away” discharge if the density decays to a critical one, in which the confinement of plasma (exactly supper thermal electrons) is better than that in normal discharge. The confinement of plasma and the anomalous Doppler instability during slide-away discharge gas puffing are investigated. The effect of gas puffing on runaway electrons during slide-away discharge is also studied in this paper. It is found that the anomalous Doppler instability can be suppressed by the gas puffing during slide-away discharge, while the confinement of plasma becomes poor, and many high energy runaway electrons occur during gas puffing.

Effects of external magnetic field and temperature on low frequency photonic band width in cryogenic superconducting photonic crystals

Li Chun-Zao,Liu Shao-Bin,Kong Xiang-Kun,Bian Bo-Rui,Zhang Xue-Yong
Acta Physica Sinica. 2012, 61 (7): 075203 doi: 10.7498/aps.61.075203
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Superconducting photonic crystals are artificial periodic structures composed of superconductors and dielectric structures. In this paper, the transfer matrix method(TMM) is used to study the transmittance of one-dimensional photonic crystals consisting of cryogenic superconductor and lossless dielectric for TM wave. It is shown that a stop band staring from zero frequency can be apparently observed, whose cutoff frequency is adjusted by varying the temperature and the magnetic field. However, because of the contribution of the normal conducting electrons (NCEs) , taking no account of external magnetic field, the width of the low frequency photonic band gap (PBG) is no longer influenced by the temperature of the superconductor. The cutoff frequency of PBG adjusted by the temperature and the external magnetic field with the contribution of NCEs are compared with those obtained by neglecting them. However, when superconductors are in a normal state, the low frequency PBG of photonic crystals disappears.

Application of floating microwave resonator probe to the measurement of electron density in electronegative capacitively coupled plasma

Zou Shuai,Tang Zhong-Hua,Ji Liang-Liang,Su Xiao-Dong,Xin Yu
Acta Physica Sinica. 2012, 61 (7): 075204 doi: 10.7498/aps.61.075204
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In electronegative or reactive plasmas, the problems such as negative ions floating near the sheath edge or deposition contamination cause more challenges for the diagnosis of conventional Langmiur probe. The electron density measured by microwave resonance probe is only a function of dielectric constant of plasma, there should be less or no influence of electronegative or reactive plasma. In this paper, a floating microwave resonator probe is proposed to measure electron density of capacitively coupled Ar plasma. A comparison with Langmuir double probe measurement shows that microwave resonance probe is applicable for measuring low electron density of plasma. The experimental results from the measurements of Ar/SF6 and SF6/O2 capacitively discharge driven by 40.68 MHz show that addition of SF6 into Ar plasma reduces the electron density significantly, with further increase of SF6 flow rate, electron density shows a gradual decrease. While for the addition ofO2 into SF6 discharge, the electron density continuously decreases with the increase ofO2 flow rate. Additionally, the electron density does not vary with lower frequency input power for SF6/O2 capacitively discharge driven by 40.68 MHz/13.56 MHz. The preliminary interpretations of the above experimental phenomena are presented.

Simulation of interaction between dust particles and plasma sheath and its distribution

Wu Jing,Liu Guo,Yao Lie-Ming,Duan Xu-Ru
Acta Physica Sinica. 2012, 61 (7): 075205 doi: 10.7498/aps.61.075205
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Collisionless steady plasma sheath model is taken into account to study the interaction between dusty particles and plasma sheath as well as the density distributions of electrons, ions and dusty particles. Numerical simulation results are obtained, showing that the ability of an isolated charge to absorb electrons weakens with the increase of dusty particle density and its temperature, while the collective effect strengthens with the radius of dusty particle. Simultaneously, Bohm velocity and the sheath thickness are also greatly affected. The sheath potential decreases significantly and the E-field is stronger near the electrode. In addition, the densities of electrons and ions reduce exponentially but the dusty particle has a critical value. The three particles satisfy the quasi-neutrality condition.

X-ray source generation under laser-Ar cluster interaction

Sun Yan-Qian,Chen Li-Ming,Zhang Lu,Mao Jing-Yi,Liu Feng,Li Da-Zhang,Liu Cheng,Li Wei-Chang,Wang Zhao-Hua,Li Ying-Jun,Wei Zhi-Yi,Zhang Jie
Acta Physica Sinica. 2012, 61 (7): 075206 doi: 10.7498/aps.61.075206
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Bright K-shell X-ray emissions are generated through the interaction between intense femtosecond laser pulses and Ar clusters. The total yield of K-shell X-ray photons reaches 1× 1011 photons/shot with a conversion efficiency of 2.8× 10-5 in 4π. When Ar clusters are irradiated by a laser pulse with intense prepulse, the yield of K-shell X-ray photos will decrease due to prepulse ionization. Keeping high-density plasmas interacting with the main pulse is essential for obtaining the highest X-ray yield.

The bubble velocity research of Rayleigh-Taylor and Richtmyer-Meshkov instabilities at arbitrary Atwood numbers

Tao Ye-Sheng,Wang Li-Feng,Ye Wen-Hua,Zhang Guang-Cai,Zhang Jian-Cheng,Li Ying-Jun
Acta Physica Sinica. 2012, 61 (7): 075207 doi: 10.7498/aps.61.075207
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We generalize the Layzer's bubble model to the cases of two-dimensional and three-dimensional analytical models of an arbitrary interface Atwood number and obtain self-consistent equations. The generalized model provides a continuous bubble evolution from the earlier exponential growth to the nonlinear regime. The asymptotic bubble velocities are obtained for the Rayleigh-Taylor(RT) and Richtmyer-Meshkov(RM) instabilities. We also report on the two-dimensional and the three-dimensional analytical expressions for the evolution of the RT bubble velocity.

Fiducial system for the diagnosis of temporal evolution of radiation fluxes with soft-X-ray spectrometer in inertial confinement fusion experiments

Song Tian-Ming,Yi Rong-Qing,Cui Yan-Li,Yu Rui-Zhen,Yang Jia-Min,Zhu Tuo,Hou Li-Fei,Du Hua-Bing
Acta Physica Sinica. 2012, 61 (7): 075208 doi: 10.7498/aps.61.075208
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In inertial confinement fusion experiments, a fiducial system is established in order to correlate the signals from different channels of one spectrometer and the signals from different spectrometers to obtain time-related experimental data. The constitution, the principle and the data processing method, together with the uncertainty analysis are introduced. Signals from different channels and from three spectrometers diagnosing from different directions are correlated with an uncertainty of 70 ps. The time-related historical radiation fluxes from a cylinder target, measured from three different directions, are obtained in the experiments on Shenguang Ⅲ prototype laser facility, offering the physical information about the heat wave propagation along the axis of the cylinder and the attenuation of soft X-ray radiation flux.

Study on the mechanism of Hall effect thruster discharge with bistable state

Han Ke,Jiang Bin-Hao,Ji Yan-Chao
Acta Physica Sinica. 2012, 61 (7): 075209 doi: 10.7498/aps.61.075209
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Experimental results indicate that there exist two stable discharge operation points in a self-excited mode Hall effect thruster. During the operation, the discharge operation point jumps to and fro between two values, which greatly influences the physical process of plasma discharge in the thruster channel and the comprehensive performance of thrusters. In this paper, by using the relationship between discharge magneto-ampere characteristic curve and magnetic field coil current curve, we propose the physical mechanism of forming the discharge bistable characteristic. On the basis of the mechanism, a method of stabilizing the single discharge operation point is presented through changing the slope of magnetic field coil current curve. The physical explanation is given through established one-dimensional dynamic fluid model for self-excited mode, and the results are approved by the self-excited experiment.

The influence of Hall drift to the ionization efficiency of anode layer Hall plasma accelerator

Geng Shao-Fei,Tang De-Li,Qiu Xiao-Ming,Nie Jun-Wei,Yu Yi-Jun
Acta Physica Sinica. 2012, 61 (7): 075210 doi: 10.7498/aps.61.075210
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The Hall drift of electrons in anode layer plasma accelerator is analyzed based on Lorentz transformation. It is shown that Hall drift does not exist always in the cross-field. If the ratio of E to B is lager than light speed, Hall drift will disappear. The further analysis shows that the Hall drift is not always in the form of gyration. It is also in the forms of wave and straight line, depending on electric-magnetic field configuration and initial energy of electrons. The electric-magnetic configuration determines the speed of drift, and then affects electron energy. This can determine the ionization efficiency in discharge. A numerical simulation using the Particle-in-Cell method is performed. The result indicates that a nice ratio of E and B will produce high ionization efficiency (for argon, this value is about 4×106). This value will change with working gas according to the ionization cross section determined by electron energy.

Plasma parameters of square superlattice pattern in a dielectric barrier discharge

Chen Jun-Ying,Dong Li-Fang,Li Yuan-Yuan,Song Qian,Ji Ya-Fei
Acta Physica Sinica. 2012, 61 (7): 075211 doi: 10.7498/aps.61.075211
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Dielectric barrier discharge is an important method of producing nonequilibrium low-temperature plasma. Measurement of the plasma parameters is highly valuable for its industrial application. Plasma parameters of square superlattice pattern are investigated by optical emission spectroscopy in a dielectric barrier discharge by using a two-liquid-electrode dielectric barrier discharge device in argon at atmospheric pressure. It is found that the light intensity of the large diameter microdischarge channel(big dot) is different from that of the small diameter channel (small dot). Vibrational temperature is investigated by using the N_{2} second positive spectrum. Electronic excitation temperature is measured by means of spectral line intensity ratio. Electron density is obtained by using the stark broadening of Ar atom 696.54 nm spectral line. The results show that the electron density and the vibrational temperature of the small dot are larger than those of the big dot but the electronic excitation temperature is lower than that of the big dot. It is suggested that the plasma state of the big dot is different from that of the small dot in the stable square superlattice pattern.

The fluorescence feature of plasma induced by femtosecond laser pulses in air

Guo Kai-Min,Gao Xun,Hao Zuo-Qiang,Lu Yi,Sun Chang-Kai,Lin Jing-Quan
Acta Physica Sinica. 2012, 61 (7): 075212 doi: 10.7498/aps.61.075212
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Effects of focusing conditions on femtosecond laser induced plasma fluorescence in air are investigated by using different focal length lenses. Under the tightly focusing condition, the fluorescence spectra are composed mainly of continuous spectrum and line spectra from N and O atoms, which is due to the higher laser intensity and corresponding higher electron density than those in the case of weakly focused laser beam. In the latter case, only line spectra from air molecules are observed. Besides, the intensity of line spectrum as a function of propagation distance is measured, which reveals the evolution of the plasma filaments.

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